In a conventional engineering tool for a programmable logic controller, in order to display a sequence-program edit screen and a unit-parameter setting screen, a selection is performed from a tool menu or a project list (a navigation window). That is, every time a program is edited or a parameter is set, a mouse (a pointer) is moved from the program edit screen or the parameter setting screen to the menu or the navigation window to select a display object. Therefore, the work efficiency at the time of editing the program or setting the parameter is decreased.
In view of such a problem, for example, Patent Literature 1 describes a technology related to a plant monitoring control device that displays plant facility operation statuses and measurement values. In this technology, only by specifying an arbitrary position on a screen by a mouse and rotating a scroll wheel (a mouse wheel) to issue a magnification (zoom-in operation) instruction and a reduction (zoom-out operation) instruction, the screen is magnified or reduced while centering on the specified position. When the rate of the magnification or reduction exceeds a set value, an optimum screen including information required by a user is provided to the user by switching the screen to a detailed view or a schematic diagram.